Conventional automobiles have three primarily hydromechanical actuators: hydraulic steering assist, hydraulic transmission, and hydraulic brakes. This hydraulic machinery is operated by arms moving a steering wheel and legs moving foot pedals. Arms, legs, steering wheel, and foot pedals all have significant inertia, and therefore relatively slow operating times. However, their slow operation is a good speed match for the slow response times of hydraulic steering, transmission, and brakes.
The typical electric vehicle (EV) has three primarily electromechanical actuators: electric power steering, electric motor propulsion, and electric regenerative braking (plus hydraulic brakes as backup). This electric machinery is also operated by arms moving a steering wheel and legs moving foot pedals. However, the slow operation of arms, legs, steering wheel, and foot pedals is a poor speed match for the fast response times of electric steering, propulsion, and braking.
Arms and legs moving a steering wheel and pedals are too cumbersome and slow to fully exploit the responsiveness of an EV's electric machinery. Automobile manufacturers have tried several alternatives, mainly the 2 degrees of freedom (DoF) tilt joystick. A 2 DoF tilt joystick is more nimble and faster to operate than a steering wheel and pedals, but it is not used in EVs because it is still not fast enough, and it has low steering precision.
A 2 DoF tilt joystick can be operated more nimbly than a steering wheel. However, like the steering wheel, it requires significant movement of the driver's entire arm. This is due to its pivot point being located below the driver's wrist. This pivot location simplifies the design and construction of the tilt joystick and makes it a very compact controller, but the required arm movement means it is not much faster than a steering wheel.
A typical steering wheel has a rotational range up to 900 degrees lock to lock—all the way left to all the way right. Using a steering wheel, a driver can turn an automobile through its entire range of steering and still make precise steering adjustments at any steering angle. A 2 DoF tilt joystick's maximum practical tilt range around its pivot point is about 90 degrees in any direction, or one tenth that of a steering wheel. This limited tilt range makes precise steering adjustments with a 2 DoF joystick very difficult to achieve over the entire range of steering. Because of its minimal speed advantage and low precision steering, the 2 DoF tilt joystick is not compelling enough to replace the mature technology of the steering wheel.
While some three degree of freedom joysticks do exist, there is a need in the art for devices which are simple to manufacture, reliable, and accurately transcribe motion in three directions.